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There are several types of urinary catheters available. The top catheter
is a stainless steel catheter used only in female dogs. It is sometimes
called a "bitch" catheter. The second catheter from the top of the
screen is a Foley catheter.
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Foley catheters have an inflatable bulb at the end that can be filled
with air or fluid (~3-5 ml) to retain the tip of the catheter within the
bladder. Foley catheters are too short to reach the bladder of male
dogs. The third catheter is a semi-rigid plastic (polypropylene) urinary
catheter. This catheter type can be used in either sex. The bottom
catheter is a red rubber feeding tube that can be used as a urinary
catheter in either sex dog. The smaller diameter red rubber catheters
(<10 Fr)may not be long enough to reach the bladder of large male
dogs. |
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Foley
Catheter: The syringe is
attached to an adapter which is attached to a thin tube within the catheter. Fluid or air
is injected into this tube which terminates in a thin walled balloon. The balloon capacity
is printed on the white plastic adapter (a) (usually 3 to 5 ml). The balloon is inflated
when the catheter is in the lumen of the bladder (b). The intent is to retain the catheter
in the bladder. The balloon is deflated prior to catheter removal by aspirating back the
fluid or air. The adaptor contains a valve which prevents loss of fluid or air.
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Urinary catheters are sized
using French (fr) units. The French number divided by 3 is the outer diameter of the
catheter in milimeters.
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The rounded tip of the catheter reduces urethral trauma as
the catheter is passed. Urine enters the lumen of the catheter through two "eye"
holes. |
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Polypropylene and rubber
catheters can be gas sterilized. The autoclave packaging can be used to maintain sterility
of the catheter while it is being passed into the urethra. A finger tab about 1 inch wide
is cut or torn from the end of the package closest to the rounded tip of the catheter, ~2
inches from the end of the package. |
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The finger tab is cut free of
the reminder of the package. The end of the package closest to the rounded end of the
catheter is removed, taking care not to contaminate the exposed end of the catheter. The
finger tab is used to guide the catheter into the urethra. |
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The tip of the
catheter should be lubricated with a water soluble lubricant to minimize urethral trauma.
The individual packages of lubricant are prefered over multiple use tubes. The multiple
use tubes may become contaminated and be a source of contamination of the urinary tract
during catheterization. |
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The penis is extruded from the
prepuce and is cleansed with an antiseptic solution such as BetadineTM or NovalsanTM. The
finger tab is used to hold the catheter as it is being introduced into the urethra. |
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The
urethra is limited in distensibility by the os penis
surrounding it's dorsal surface. The catheter tends toward taking a
straight course at the ischial arch
. The catheter can be palpated in the perineal region. You can gently push
on the catheter through the skin in the perineal region to guide the catheter around the
arch. |
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A
sterile hemostat can be used to feed the catheter out of the sterile package. |
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Female dogs can be catheterized by digitally palpating the urethral orifice, then
passing the catheter under your finger...
or a speculum can be
used to visualize the urethral orifice. These are human nasal specula but work well as
canine vaginal specula. The one on the bottom has blades approximately 3/4 of an inch
long. The blades are too short to aid in visualization of the urethral orifice in most
bitches. The blades of the top speculum are approximately 2 inches long. |
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When
using a vaginal speculum, the blades are initially directed vertically until the clitoral
fossa is passed and then they are redirected horizontally. The handles of the speculum
should be pointed towards the tail so they are not in the operator's way as they are
passing the urethral catheter. |
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This is an anal scope that works well to visualize the urethral orifice. The
speculum (a) and rounded tip insertion guide (b) are lubricated and inserted into the
vagina. The insertion guide is removed by pulling on the metal ring (c) attached to the
guide. The light source (d) is turned on. The speculum is slowly retracted until the
urethral orifice is visualized. The urinary catheter is passed into the bladder and then
the speculum is removed. If the urethral orifice is not visualized, reinsert the insertion
guide into the speculum before advancing the speculum into the vagina. Note the edge of
the speculum is sharp. |
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This is what the
view looks like through the scope. The arrow points to the urethral orifice. The other two
lines in the vaginal mucosa are folds in the tissue. Some bitches have a prominant mound
of raised tissue around the urethral orifice. Gently probe the urethral orifice with the
urinary catheter to confirm that it is the urethral orifice and not a fold of tissue.
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An otoscope with a large (wide but short) cone works well
as a vaginal speculum to visualize the urethral orifice in the bitch. This is a Foley
catheter being placed throughthe otoscope. Unfortunately, the flare end of the Foley will
not fit through the otoscope cone and you need to disconnect the cone (a) from the light
source (b) and leave the cone with the catheter until the catheter is removed from the
patient. The letter (c) points to a magnifying lens attached to the light source.
Magnification makes it easier to see the urethral orifice. |
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A 3 1/2 French
polypropylene catheter will fit through the lumen of the Foley catheter to increase its
rigidity and make it easier to pass. |
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You can use a stainless steel catheter as a stylet for a Foley catheter. The
steel catheter is fitted into the eye of the Foley and the two are passed together into
the bladder. This technique can only be used with "larger" (~12 French or
larger) Foley catheters as the steel catheter will not fit in the eyehole of smaller
Foleys. Lubrication of the metal catheter before it is inserted into the eyehole makes
both insertion and removal of the metal catheter easier. The Foley bulb is inflated and
the metal catheter is removed. If you fail to inflate the bulb of the Foley catheter
before pulling out the metal catheter, both catheters will be removed. |
A rigid metal
catheter should never be over-inserted into the bladder as it may penetrate through the
apex of the bladder.
Gentle technique is always called for when
passing urinary catheters but this is especially true when using rigid catheters.
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